Method for automatically monitoring and servicing the drilling fluid condition in a well bore

ABSTRACT

This invention automatically monitors and services the drilling fluid condition of a well bore during drill pipe withdrawal by determining the amount of fluid required to replace the amount of steel removed therefrom. The required volume of fluid is then compared with the volume of fluid pumped into the borehole during the fluid refilling operation. The result of this comparison is used, among other things, to monitor kick or loss conditions which may occur during drill pipe withdrawal.

[ 1 Mar. 7, 1972 Primary Examiner.lerry W. Myracle Attorney-Michael P.Breston and Alfred B. Levine [57] ABSTRACT This invention automaticallymonitors and services the drilling fluid condition of a well bore duringdrill pipe withdrawal by determining the amount of fluid required toreplace the amount of steel removed therefrom. The required volume offluid is then compared with the volume of fluid pumped into the boreholeduring the fluid refilling operation. The result of this comparison isused, among other things, to monitor kick or loss conditions which mayoccur during drill pipe withdrawal.

l2 QlnimsJDrawingllgu res United States Patent Leonard MONITORING ANDSERVICING THE DRILLING FLUID CONDITION IN A WELL BORE [72] Inventor:Loren W. Leonard, 8345 Triola, No. 33,

Houston, Tex. 77036 Aug. 28, 1970 Field References Cited STATES PATENTSA 7/124; M Crites 54] METHOD FOR AUTOMATICALLY [22] Filed:

[21] Appl.No.: 67,706

[51] lnLCI................ [581 MUD TANK 3 llllll l \5 2 e e 4 m a T 2A, n 3 5 a 6 R 6 o 3 R ED W ED 0 L as. 6 an 4 A aw T a U MN 5| mm A LMMm TU 00 F OD V0 SN V W VP C c 5 5 ,s m v 7 METHOD FOR AUTOMATICALLYMONITORING AND SERVICING THE DRILLING FLUID CONDITION IN A WELL BOREBACKGROUND OF THE INVENTION It has been well established that many ofthe blowouts that occur during drilling operations are caused by areduction of hydrostatic pressure during drill pipe withdrawal, commonlyknown as a trip". To maintain adequate hydrostatic pressure after orduring each trip, it is important to pump, through the fill line of adrilling fluid (mud) circulation system, a volume of mud which isdetermined from the amount of steel withdrawn, which is in turndetermined from the number of drill pipes and collars withdrawn.

If the amount of mud required is substantially equal to the amount ofmud pumped into the borehole, the operation is assumed to be normal. Ifthe amount of mud pumped into the borehole is less than the volumerequired to replace the amount of steel withdrawn, then some other fluidenters the borehole either from the formation itself or from anothersource. Such a gain of fluid is known as a kick condition. Conversely,if the volume of mud pumped into the hole is greater than the volume ofmud required to replace the amount of steel withdrawn, then mud is beinglost from the borehole to the formation or to another space.

SUMMARY OF THE INVENTION It is a general object of this invention toprovide an automatic mud refilling method allowing an early warningalert as to the existence of a kick or loss condition. It is a morespecific object of this invention to provide a new and improved methodfor monitoring the condition of a well during tripping. The new methodis economical, reliable in operation, and can be carried out even by arelatively unskilled driller within a minimum of time, therebysubstantially reducing the cost and hazard of the trip. With the newmethod the driller is free to attend to chores connected with operationsother than those required to refill the borehole.

A preferred method of this invention comprises: obtaining an electriccount of the number of pipe stands pulled during each trip, multiplyingthe count by a scaling factor dependent upon the particular wellcharacteristics to'obtain the volume of fluid required, comparing thevolume required with a metered quantity of fluid pumped into the fillline in order for the fluid in the borehole to reach a normal referencefluid level, and using the result of this comparison to obtain anindication with respect to kick and loss conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic illustrationof a suitable system for carrying out the preferred method of thisinvention; and

FIG. 2 illustrates the use of a manual counter for providing a scalingfactor into the system of FIG. 1.

FIG. 1 illustrates a conventional well being drilled which typicallyincludes a conductor casing 10, a wellhead I2, and conventional blowoutpreventers l4 and 16. A pump 18, which can conveniently be thecirculating centrifugal pump of the existing mud system that circulatesthe fluid or mud in a mud tank or pit 22 through a circulating fluidline 24, is selected to refill the borehole with mud. Accordingly, thefill line 25 is connected to a three-way valve 30 of the typemanufactured by Rockwell Manufacturing Company, Model 3464. Ordinarilyvalve 30 establishes fluid communication between ports 26 and 27 in line24 and upon becoming actuated by a line 28, which can be an electricline or an air line, valve 30 breaks fluid communication between ports26 and 27 and establishes fluid communication between ports 26 and 29.Since the construction and operation of such a three-way valve 30 iswell known in the art, no further description thereof is believednecessary.

To measure the amount of fluid pumped through the fill line 25 forpassage downwardly through the casing 10, there is provided in fill line25 a conventional fluid meter 32, the readout of which is preferably anelectric signal fed via line 33 as hereinafter described. One such fluidmeter is manufactured by the Foxboro Company and known as a MagneticFlow Transmitter, another is manufactured by Rotron, Inc., and known asa Velocity Flowmeter. A return line 34 returns the fluid back to the mudtank 22 in conventional fashion. Mounted on the derrick floor 36 are arotary table 37 of conventional design and a suitable monitoring andalarm system, generally designated as 40.

System 40 is preferably a digital system to provide faster response andgreater versatility. It will be understood however that this inventionis not limited to any particular system and that an analog rather than adigital system could be equally employed, as will be apparent to thoseskilled in the art. The components forming system 40 can be purchasedfrom various manufacturers, such as Foxboro, Co., Atek Inc., MasterSpecialties Co., etc.

Above the derrick floor 36 are the elevators 42, which are coupled onone hand to the drill stand, generally designated as 44, desired to bewithdrawn, and to a book 46 on the other hand. Hook 46 is carried by ablock 48 in conventional manner. As will be understood by those skilledin the art, each pipe stand 44 normally comprises a number, say three,of drill pipe joints 45.

To count the number of pipe stands 44 withdrawn by block 48, there isprovided a stand detector 50 which detects the passage and removal ofeach stand and provides an appropriate electric signal onto line 51 toadvance-the count in a stand counter 52. The stand detector 50 may be amechanical system, an electromechanical system, or an optical systememploying a light beam and photocells. The electromechanical systemwould include microswitches for closing an electric circuit after thepassage of each pipe stand. Whichever system is employed for the standdetector 50, line 51 can be made to receive a number of pulses equal tothe number of pipe stands withdrawn. This number, illustrated as 3, isdisplayed in the window of the stand counter 52.

A volume required counter 56, which may be solid-state, electronic,digital multiplier device, manually receives a sealing factor through aknob 57, which is determined from the parameters of the particular wellbeing refilled. Counter 56 multiplies this scaling factor by the numberor count of stands pulled. The count of stands pulled is received on aline 58 from the stand counter 52. The number illustrated in the windowof counter 56 is 1.77 barrels for the three stands pulled by the block48.

This volume required is the volume of fluid necessary to fill theborehole up to a reference level, which is detected by a normal mudlevel detector 60, in order to replace the volume of steel withdrawnfrom the borehole. If after pump I8 delivers to the fill line 25 anamount of fluid equal to the volume required and the fluid level in theborehole is still below the normal level required, the pump willcontinue to deliver fluid into the borehole and an alarm or warningsignal will be given as hereinafter described. If, after the pump hasdelivered the required volume of fluid into the borehole, the fluid inthe borehole suddenly rises above the normal level a high-level,detector 61 will detect the rise in the fluid level to also provide awarning signal.

As previously mentioned, the readout of the fluid meter 32 is anelectrical signal on line 33 applied to a volume pumped counter 62 whichindicates the volume of fluid actually delivered downwardly into theborehole through the fill line 25. This delivered volume is displayed inthe window of counter 62. With the figures previously selected andassuming normal operation, the volume delivered is also L77 barrels.

A suitable comparator 64 receives the count from the volume requiredcounter 56 on line 66 and the count from the volume pumped counter 62 online 68. Comparator 64 compares the counts received on lines 66 and 68.The result of that comparison will be a zero output which will beindicated by a "normal" indicating device 70, in the event that thevolume required is substantially equal to the volume pumped. If thevolume pumped is greater than the volume required, comparator 64 willprovide an output signal to a loss" indicating device 72. lf the volumepumped is less than the volume required, a kick" indicating device 74will become actuated.

Referring now to FIG. 2, to facilitate the driller to obtain therequired scaling factor for manual insertion by knob 57 in the volumerequired counter 56, there is provided a simple, convenient,hand-operated counter 80 having a rotatable drum 82 which is rotatedmanually by a knob 84. The operator selects in window 86 the particularphysical parameters for the pipe stands being pulled. After selectingthe proper parameters, say 4% inch-OD pipe having 16.60 lbs./ft., theproper scaling factor will appear opposite to the number of feet of pipepulled. In the example illustrated, for 93 feet of drill pipe pulled,which corresponds to one stand, the required volume will be 0.59barrels. It is this amount which is the scaling factor to be insertedinto the volume required counter 56.

In operation, the circulating centrifugal pump 18 ordinarily circulatescontinuously the mud in the mud pit 22 through line 24. Pump 18 is arelatively low-pressure, high-volume pump as compared to the relativelyhigh-pressure, high-volume, extremely bulky stroke pump (not shown)conventionally employed to fill the borehole. Prior to startingoperations, the operator selects, in the manner previously described,the suitable scaling factor and inserts it into the volume requiredcounter 56. After the operator initiates the stand withdrawal operation,the stand detector 50 detects the passage of each stand and the count inthe stand counter 52 increases by one. After stand detector 50 hasdetected three stands, the reading in the window of the stand counter 52will be 003 and the reading in the volume required counter 56 will be1.77.

For the numbers illustrated, after the stand counter 52 has counted 003,a signal will be supplied from the volume required counter 56 via a line53 to a valve control mechanism 55 for suitably actuating the three-wayvalve 30. This actuation is effected via line 28 and causes thethree-way valve 30 to break fluid communication between ports 26 and 29,thereby commencing the refilling operation through the fill line 25 andthe metering operation by the fluid meter 32.

Assuming that the refilling operation is normal, after the fluid meter32 has measured a volume pumped equal to the volume required, the fluidlevel in the borehole will be at the reference level, as detected by thenormal level detector 60. If the volume pumped to reach the referencelevel is greater than the volume required as determined by thecomparator 64, the loss warning light 72 will become actuated. If thevolume pumped is less than the volume required, a kick lamp 74 willbecome actuated. Finally, if the volume required is equal to the volumepumped, the normal lamp 70 will become actuated. After pump 18 deliversthe required volume of fluid downwardly into the borehole up to thereference level, the normal level detector 60 will provide a signal vialine 63 to the valve control device 55 for actuating the three-way valve30, thereby breaking fluid communication between ports 26 and 29, andreestablishing fluid communication between ports 26 and 27. Counters 52,56 and 62 will then begin the next withdrawal cycle and cumulate thecounts. On the other hand, it will be appreciated that the counters canbe arranged to become reset after each cycle of operation.

If after the three-way valve 30 has switched back to its normalcondition, whereby fluid communication is established between ports 26and 27,, there should occur a sudden rise in the fluid level above thereference level, the high-level detector 61 will provide a signal to awarning lamp 71 via line 73.

While in the above description of system 40 and of the mud fillingsystem, specific reference was made to particular component parts andsubassemblies, it will be appreciated that variations are possible. Forexample, pump 18 need not be the mud circulating pump of the mud pit 22.Instead, a pump independent of the mud circulation system can beemployed for pumping fluid from pit 22 into casing and, hence, thethreeway valve 30 can be eliminated. Also, other means can be used tomeasure the volume of steel withdrawn which determines the volumeoffluid required. The means 50 for counting the pipe stands arepositioned preferably on the sidewall of the derrick at a distance abovethe derrick floor 36 substantially equal to a pipe stand.

What I claim is:

l. A method for filling a well bore with drilling fluid to replace thevolume of material withdrawn while tripping comprising the steps of:

a. determining the volume of material withdrawn during each trip;

b. delivering to the borehole a volume of drilling fluid dependent uponthe volume of material withdrawn;

0. measuring the volume of fluid delivered in step (b);

d. comparing the volume of material withdrawn from step (a) with themeasured volume of fluid delivered from step (c); and

e. using the result of the comparing step (d) to obtain an indication ofthe fluid condition in said well bore.

2. A method for filling a well bore with drilling fluid to replace thevolume of material withdrawn while tripping comprising the steps of:

determining the volume of fluid required to replace the volume ofmaterial withdrawn during each trip;

delivering to the borehole a volume of drilling fluid in dependence uponthe fluid level in the borehole relative to a reference point; and

comparing said volume of fluid required with said volume of fluiddelivered to obtain an indication of the fluid condition in said wellbore.

3. The method of claim 2 wherein said volume of fluid required isdetermined by counting the number of pipe stands withdrawn from the wellbore during each trip.

4. The method of claim 3 wherein said number of pipe stands withdrawn ismultiplied by a scaling factor dependent upon the characteristics of thepipe stands withdrawn to obtain said volume of fluid required.

5. The method of claim 4 wherein said volume of fluid delivered ismeasured by a fluid meter positioned in the fluid fill line leading tosaid well bore.

6. The method of claim 5 wherein the fluid is delivered to the well boreby a circulating pump associated with the mud pit.

7. The method of claim 6 wherein said circulating pump delivers fluid tosaid pit and to said well bore through a threeway valve.

8. The method of claim 2 and further including the steps of:

monitoring at said reference point the fluid level in said well bore toobtain a control signal; and

using said control signal to control the delivery of said drilling fluidto said well bore.

9. A method for detecting the condition of a well by controlling, whiletripping, the drilling fluid in said well and providing an early warningindication of an abnormality in said well characterized by:

a. measuring from the volume of solid materials moved during each trip arequired volume ofdrilling fluid;

b. delivering a measured volume ofdrilling fluid in order to restore inthe well the drilling fluid to a reference level;

c. comparing said required volume with said measured volume; and

d. obtaining from the comparing step (c) signals which are indicative ofthe condition of said well.

10. The method of claim 9 wherein said measured volume is measured by afluid flowmeter.

11. The method of claim 9 wherein said required volume is measured byobtaining a count of the number of units of said solid materials moved,and multiplying the count by a scaling factor dependent upon thephysical characteristics of said units of solid material.

12. The method of claim 11 and monitoring said reference level in saidwell to obtain a first control signal, and using said first controlsignal to determine said measured volume.

1. A method for filling a well bore with drilling fluid to replace thevolume of material withdrawn while tripping comprising the steps of: a.determining the volume of material withdrawn during each trip; b.delivering to the borehole a volume of drilling fluid dependent upon thevolume of material withdrawn; c. measuring the volume of fluid deliveredin step (b); d. comparing the volume of material withdrawn from step (a)with the measured volume of fluid delivered from step (c); and e. usingthe result of the comparing step (d) to obtain an indication of thefluid condition in said well bore.
 2. A method for filling a well borewith drilling fluid to replace the volume of material withdrawn whiletripping comprising the steps of: determining the volume of fluidrequired to replace the volume of material withdrawn during each trip;delivering to the borehole a volume of drilling fluid in dependence uponthe fluid level in the borehole relative to a reference point; andcomparing said volume of fluid required with said volume of fluiddelivered to obtain an indication of the fluid condition in said wellbore.
 3. The method of claim 2 wherein said volume of fluid required isdetermined by counting the number of pipe stands withdrawn from the wellbore during each trip.
 4. The method of claim 3 wherein said number ofpipe stands withdrawn is multiplied by a scaling factor dependent uponthe characteristics of the pipe stands withdrawn to obtain said volumeof fluid required.
 5. The method of claim 4 wherein said volume of fluiddelivered is measured by a fluid meter positioned in the fluid fill lineleading to said well bore.
 6. The method of claim 5 wherein the fluid isdelivered to the well bore by a circulating pump associated with the mudpit.
 7. The method of claim 6 wherein said circulating pump deliversfluid to said pit and to said well bore through a three-way valve. 8.The method of claim 2 and further including the steps of: monitoring atsaid reference point the fluid level in said well bore to obtain acontrol signal; and using said control signal to control the delivery ofsaid drilling fluid to said well bore.
 9. A method for detecting thecondition of a well by controlling, while tripping, the drilling fluidin said well and providing an early warning indication of an abnormalityin said well characterized by: a. measuring from the volume of solidmaterials moved during each trip a required volume of drilling fluid; b.delivering a measured volume of drilling fluid in order to restore inthe well the drilling fluid to a reference level; c. comparing saidrequired volume with said measured volume; and d. obtaining from thecomparing step (c) signals which are indicative of the condition of saidwell.
 10. The method of claim 9 wherein said measured volume is measuredby a fluid flowmeter.
 11. The method of claim 9 wherein said requiredvolume is measured by obtaining a count of the number of units of saidsolid materials moved, and multiplying the count by a scaling factordependent upon the physical characteristics of said units of solidmaterial.
 12. The method of claim 11 and monitoring said reference levelin said well to obtain a first control signal, and using said firstcontrol signal to determine said measured volume.